United States
Environmental Protection
Agency
Atmospheric Sciences
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S3-87/034 Jan. 1988
Project Summary
A Sensitivity Analysis  and
 Preliminary Evaluation of RELMAP
 Involving  Fine and Coarse
 Paniculate Matter
Brian K. Eder
  In response to the new, size dis-
criminate federal standards for Inhalable
Particulate Matter, the Regional Lagran-
gian Model of Air Pollution (RELMAP)
has been  modified to include simple,
linear parameterizations which simulate
the chemical and physical processes of
fine and coarse particulate matter.
  Because these  new, simplified  pa-
rameters are only accurate to a limited
degree, they  may be upgraded or re-
placed in the future with more sophisti-
cated parameters as further research is
conducted. As an initial step in this
possible refinement, RELMAP has been
subjected to  a sensitivity analysis in
which the effect of inducing a +/- 50%
change in the three major parameteriza-
tions (transformation  rate and wet and
dry deposition rates)  involving the
simulation of fine and coarse particulate
matter has been examined. Simulated
concentrations of fine and coarse par-
ticulate matter proved to be most sensi-
tive to the wet deposition of fine and
coarse particulate matter, respectively;
fine concentrations were  somewhat
sensitive to the transformation rate of
sulfur dioxide (SO2) into sulfate 1SO4=),
and less sensitive to the wet deposition
of SO2, and the dry deposition of fine
particulate matter and SO2; and finally
coarse concentrations were somewhat
sensitive to the dry deposition of coarse
particulate matter.
  In order to assess the model's abilities,
and to determine just how accurately
these  new parameters  simulate  the
actual physical and chemical processes
of the atmosphere, RELMAP was
evaluated for the summer  of  1980,
using emissions data from the NAPAP
Version 5.0 emissions inventory, moni-
toring data from the Inhalable Particu-
late Network and meteorological data
from the National Climatic Data Center.
Unfortunately, several obstacles limited
the scope of this evaluation; the two
most important being the omission of
open source emissions from the NAPAP
inventory, and the spatial and temporal
incompatibility of the IPN data. Given
the nature of these deficiencies, it is
not surprising that RELMAP signifi-
cantly underpredicted the concentra-
tions of fine and coarse particulate
matter. The model did, however, exhibit
some skill in its simulation of the con-
centrations,  producing correlation co-
efficients of 0.53 and 0.33 for fine and
coarse particulate matter, respectively.
  This Project Summary was developed
by EPA's Atmospheric Sciences Re-
search Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that Is fully docu-
mented In a separate report of the same
title (see Project Report ordering In-
formation at back).


Introduction
  The  primary National  Ambient Air
Quality Standard (NAAQS) for particulate
matter was established in 1970 with the
enactment of the Clean  Air Act. The
values of the standard were based upon
state-of-the-art  information concerning

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the health effects of ambient concentra-
tions of Total Suspended Paniculate (TSP)
matter and other environmental factors.
In 1977, the Clean Air Requirement Act
called for  a reappraisal of this NAAQS.
One reason for this reappraisal was a
shift in emphasis from TSP, which ranged
in size from 0.0 to 50.0 /urn, to  smaller,
size discriminate Inhalable Paniculate (IP)
matter, which ranged in size from 0.0 to
15.0 nm. The IP was comprised of fine
particulate matter (FINE-10),  which in-
cluded particles  less than 2.5  jum  in
diameter,  and coarse particulate matter
(COARSE-15), which  initially included
particles greater than or equal to 2.5, but
less than or equal to 15.0 M™.
  In 1981, after reviewing EPA's Clean
Air Science Advisory Committee's recom-
mendation and the concurrent  Interna-
tional Standards Organization Task Group
recommendations, the Office  of Air
Quality Planning and Standards (OAQPS)
decided that the  revised  standard for
ambient air concentrations of IP should
be based upon a 10 p.rr\ rather than a 15
/jm criteria. Therefore, COARSE-15 was
replaced by COARSE-10, which included
particles greater than or equal to 2.5 ^m,
but less than or equal to 10.0 /urn.
  As  a result  of the  revised  NAAQS
standards for ambient air concentrations
of primary particulate matter,  OAQPS
has expressed  the need  for size dis-
criminate  particulate models  in  order to
assist in regulatory planning. Shifting the
emphasis onto the smaller particles in-
creases the importance of regional scale
models. Much of the mass of the smaller
particles  results  from  gas to  aerosol
conversion which is a slow process that
occurs over  regional spatial  scales  as
opposed  to urban scales.  Therefore,  in
response to the promulgation  of the new
size discriminate federal standards for IP,
the Regional Lagrangian  Model of Air
Pollution (RELMAP) has been modified to
include simple, linear parameterizations
which simulate the chemical and physical
processes of FINE-10 (including  the con-
version of SO2 to S04=.) and COARSE-10.
 Model Background
  RELMAP  is  a  mass-conserving, re-
 gional-scale Lagrangian model that per-
 forms simulations over 1 ° by 1 ° grid cells
 covering the eastern two-thirds of the
 United States and southeastern Canada.
 Discrete puffs  of S02,  S04=,  fine and
 coarse particulate matter are released at
 twelve hour intervals from each of the
 1350 grid cells  that contain sources. The
puffs are then subjected to linear chemical
transformation and wet and dry deposition
processes as they are transported across
the model's domain. The suspended mass
and deposition for each puff is apportioned
into the appropriate grid cell based upon
the percentage of puff over that grid cell.
The rate of change in the pollutant mass
resulting from  the transformation and
wet and dry deposition process is directly
proportional to the total mass.
  Because dispersion generated by small-
scale turbulence is not nearly as  signifi-
cant as long term transport and deposition
processes for regional-scale models such
as  RELMAP, the model simulates both
horizontal and vertical diffusion through
simple  parameterizations.  RELMAP
divides the atmospheric boundary layer
into three layers. The first layer is between
the surface and 200 m,  and the second
layer is between 200 and  700 m. The
depth of the third  layer is variable,  de-
pending upon the seasonal-mean maxi-
mum mixing height,  and is assumed to
be  1150 m during the winter, 1300 m
during the spring and fall, and 1450 m
during the summer.
  During the unstable regimes of midday
periods, pollutants from both area and
point sources become well mixed up to
the mixing height  long  before they  are
transported a distance equal to the spatial
resolution  of the  grid.  Therefore,  it is
assumed that instantaneous and complete
mixing occurs within the three layers of
the model during the unstable daylight
hours. However, after sunset, when mix-
ing is  prohibited by  stable conditions,
point and area source emissions are con-
fined to the separate layers into which
they are emitted. All area source emis-
sions remain in Layer 1, within 200 m of
the surface, while  emissions from point
sources are allocated into  Layer 2,  ac-
counting for typical  plume rise, which
averages several hundred meters.
  RELMAP assumes that horizontal  dif-
fusion  of the puffs occurs at a constant
rate so that the size of the puff increases
at  a rate of 339  kmVh,  and that  the
distribution of the mass of pollutant in
the puff  remains  homogeneous at  all
times.
  RELMAP treats  fine and coarse par-
ticulate  matter as  independent non-
evolving  pollutants,  that  is  physical
and/or chemical transformation between
fine particulate matter and coarse par-
ticulate matter  is considered negligible.
RELMAP  does,  however, consider  the
transformation  of  SO?  into S04=. This
oxidation  process  varies primarily with
solar insolation (i.e. diurnally, latitudinally,
and seasonally) and with moisture
content.
  Dry deposition of S02, SO4=, fine and
coarse particulate matter is a highly vari-
able, complex process that  is parame-
terized by RELMAP as a function of land
use, season, and stability  index. Twelve
land use categories, categorized by sur-
face characteristics and vegetation type
were  gridded  to RELMAP's  1° by  1°
domain. Typical dry deposition velocities
used in the model range between 0.05
and 1.15 cm/s for S02,  and between
0.05 and 0.50  cm/s for S04= and fine
particulate matter, depending upon the
season, the stability and  the land  use
category.
  When  considering diurnal  variations,
use of the parameterizations discussed
above  is not always  recommended. In
order  to compensate for  the  high
nocturnal atmospheric resistance, when
plant absorption is minimal,  the model
assumes that dry deposition velocities
are reduced to 0.07 cm/s  for SO2, S04=
and fine particulate matter.
  Because  coarse  particulate  matter
consists  of a wide range of particle dia-
meters, two sets of dry deposition veloci-
ties are used by the model. The first set
applies to  particulate  matter with dia-
meters of  5 /urn, and the  second set
applies to particles with diameters of 10
//m. The dry  deposition  velocities for
particles with a 5 yum diameter  range
between 0.4 and 5.0 cm/s, and between
1.0 and 6.0 cm/s for the 10 /um diameter
particles. Unlike SO2, S04=, and fine
particulate matter,  the dry  deposition
velocities of coarse particulate matter are
much less dependent of the time of day
or  the  season; therefore, diurnal and
seasonal variations  are considered
negligible.
  The  complex process of wet depositior
of SO2, SO4=, and fine and coarse par-
ticulate matter is thought to be a functior
of cloud chemistry, cloud type, pollutant
concentration and precipitation type anc
rate. RELMAP, however,  parameterizes
this process quite simply, treating it onl\
as  a function of precipitation rate anc
cloud type.  The three cloud  types con-
sidered are Bergeron or cold-type clouds,
maritime or warm-type clouds, and con-
vective-type clouds. The model assumes
that all winter precipitation results frorr
the Bergeron process, that spring  anc
summer precipitation result from the
convective-type clouds, and that autumr
precipitation is confined  to  warm-type
clouds.

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Sensitivity Analysis

  The simplified parameterizations, which
were recently incorporated into the model,
are designed to simulate the complex
meteorological and chemical process in-
volving fine and coarse paniculate matter.
Because of their simplicity, they may be
upgraded or even replaced in the future
with more sophisticated parameteriza-
tions as further research is undertaken.
As an initial step in this possible refine-
ment, RELMAP was subjected to a sen-
sitivity analysis. In this analysis, variations
found in the model's output  (concentra-
tions of fine and coarse paniculate matter)
due  to changes in  the model's param-
eterizations are examined. The analysis,
which employed actual  meteorological
and  emissions data for July 1980, was
performed using the currently accepted
values for all  of the input parameters.
The  parameterizations examined in this
sensitivity analysis  included: the trans-
formation rate of S02 into S04=, the wet
and  dry deposition rates of SO2, fine
(including S04=) and coarse particulate
matter. SO2  parameterizations are in-
cluded in this analysis  because it is  a
precursor to S04=  and therefore to fine
particulate matter. With each simulation,
the values of the respective parameteriza-
tions were allowed to vary +/- 50% around
their currently accepted or nominal values.
Results of the sensitivity analysis were
recorded along a specific transect that
stretched across the model's domain from
Alabama  to Quebec.  The  sensitivity
analysis of coarse particulate matter
revealed that increasing either the wet or
dry deposition of the coarse particulate
matter results, as expected, in a decrease
in the concentration, and that  this de-
crease is more pronounced in the case of
wet  deposition. Likewise,  decreasing
either the wet or dry deposition of coarse
particulate matter results in increased
concentrations. For a 50% decrease  in
the  wet deposition, the concentration
increases an average of 30 to 50%, but
for a 50% increase in the wet deposition,
the  concentration  only decreases an
average of 15 to 25%. Similar trends are
evident, but to a lesser degree, with the
dry deposition. For a 50% decrease in dry
deposition, the concentration increases
an average of 5 to 10%, but for a 50%
increase in dry deposition, the concentra-
tion  only decreases between  3 and 6%.
  Analysis of the sensitivity  of fine par-
ticulate matter concentration to changes
in the wet and dry deposition of S02 and
fine particulate matter,  as  well  as  to
changes in the transformation rate  of
S04~, reveals many  of the same char-
acteristics  as noted with the  coarse
particulate  matter. As expected, the wet
deposition of fine particulate matter had
the largest impact upon the concentration
field. For a given 50% increase in the wet
deposition of fine particulate matter, the
concentration decreased  an average  of
15  to 30%, whereas  a 50% decrease in
the wet deposition resulted in a 30  to
50% increase in the  concentration. The
influence of  S02 wet deposition, how-
ever, proves to be minimal.
  Analysis  of the dry deposition for both
S02 and fine particulate matter, reveals
that the influence of S02 dry deposition
on  the concentration of fine particulate
matter proved to be all but non-existent.
A +/- 50% change in the SO2 dry deposi-
tion resulted in at most a +/- 1% change
in the concentration field. The impact of
fine particulate dry deposition on the fine
concentration field, though small, is more
noticeable.  Inducing a +/- 50% change in
the dry deposition  of fine particulate
matter resulted in a  3 to 6% change  in
the concentration field.
  And finally, the sensitivity of fine par-
ticulate matter concentration to changes
in the transformation rate is somewhat
significant. A 50% increase in the trans-
formation rate increases the concentration
by an average of 5 to 10%, while a 50%
reduction  in  the transformation rate
results  in a 6 to 12% decrease in the
concentration.
Preliminary Model
Performance Evaluation
  RELMAP was run for the three month
period  of July, August and September,
1980 in order  to  simulate  a summer
season  using  meteorological data ob-
tained  from the  National Climatic Data
Center located in Asheville, N. C. Input
emissions data were obtained from the
National Acid Precipitation Assessment
Program (NAPAP) Version 5.0 Emission
Inventory.  Simulated  ambient air con-
centrations of fine and coarse particulate
matter were then compared on a monthly
and seasonal basis with monitoring data
obtained from the  Inhalable  Particulate
Network (IPN) data set. Although Version
5.0 of  the  1980 NAPAP Emissions  In-
ventory represents  by far the most com-
prehensive and highest quality emissions
data set available,  it was developed  to
provide  an emissions data base  for acid
deposition research and  modeling, not
regional particulate modeling. Because
of this, less emphasis was placed on the
TSP inventory, resulting in numerous
deficiencies in both the fine and coarse
particulate  emissions. The total annual
emissions of TSP for the entire NAPAP
grid area was estimated to be 74,192
ktons with 46,560 ktons or 62.8% of the
total NAPAP TSP inventory being emitted
within the model's domain. Of this total,
90.23% can be attributed to area sources,
and 9.77%  can  be attributed to point
sources. Of the 4,550  ktons of TSP at-
tributed to point sources,  14.20% are
emitted as particles with diameters larger
than 10 /im, 7.56% are emitted as fine
panicles, 7.29% are emitted as coarse
panicles, and  70.95%  cannot be frac-
tionalized. Fractionalization  of the area
source emissions reveals  that  of the
42,010 ktons of TSP attributed to area
sources, 28.71% are emitted as coarse
particles, 27.88% are  emitted  as  fine
panicles, 42.56% are emitted as panicles
with diameters larger than  10 pm, and
0.85% cannot be fractionalized.
  These non-fractionalized  percentages
illustrates one of the major deficiencies
of the  NAPAP TSP  inventory.  A large
percentage of  the many point and area
source categories designated by NAPAP
do  not have particle size distributions.
Because of this,  more than  3,584 ktons
or roughly 7.7% of the TSP emitted from
point and area sources located within the
model's domain cannot  be fractionalized,
or broken down  into the  respective size
categories.  OAQPS is currently updating
their SCC  inventory, but until this  is
completed,  these  non-fractionalized
emissions cannot be used as input into
the model,  which will have detrimental
effects on the model's performance.
  Another, even  more serious deficiency
found with the NAPAP TSP inventory is
the  omission  of many of  the "open"
source emissions, which are described
as  sources of  air pollution  too great in
extent to be controlled by enclosure. Open
source emissions, which are extremely
difficult to  estimate, are equivalent  in
magnitude, under the most conservative
of  estimates,  to the anthropogenic
sources — yet most are  excluded from
the inventory. Examples of open sources
of TSP excluded from the inventory in-
clude: agricultural tilling, wind erosion,
construction activity, and mining opera-
tions. Estimates of those open  sources
which  are  included  in the  NAPAP in-
ventory are often much lower than other
independent estimates. For example, in-
dependent  estimates of TSP emissions
from paved and non-paved roads, which
account for over 70% of  the TSP emis-

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sions in the NAPAP inventory, are more
than an order of magnitude higher than
the NAPAP estimates.
  Because of the number and seriousness
of these deficiencies,  any model per-
formance evaluation using the NAPAP
inventory as a source of TSP emissions
must be considered preliminary at best.
Until  emissions of  TSP are given the
same consideration as those of S02, S04=
and other detrimental pollutants, model-
ing of fine and coarse particulate matter
will  continue to  lag behind the  other
modeling efforts being undertaken today.
  In  order to  adequately evaluate a
regional scale model such as RELMAP,
which has a 1 ° by 1 ° grid cell resolution,
one would  ideally  have a monitoring
network made  up of remote  locations
that have the same spatial and temporal
resolution as the model.  Unfortunately,
the Inhalable Particulate Network (IPN),
which w?s developed and implemented
by the Environmental Monitoring Systems
Laboratory  (EMSL)  in conjunction with
the Office of Air Quality Planning and
Standards (OAQPS), was  primarily de-
signed to characterize urban scale con-
centrations of suspended particulate
matter, since the attainment of air quality
standards is evaluated over this scale.
Because of this, an overwhelming majority
of the IPN  sites are classified as either
center city or  suburban, where the
dominant land use is described as either
industrial, commercial or residential.
  The IPN  became operational during
April 1979,  when 57  sites  located
throughout the United  States went on-
line using hi-vol, dichotomous and size
selective inlet samplers to collect data,
and eventually grew to 157 sites in 1981.
Unfortunately, of the 157 IPN sites that
were in operation at one time or another,
only  14 were spatially and temporally
compatible with this evaluation. A total of
41 sites were located outside the model's
domain,  and  62 sites did  not  come
"online" until after the evaluation period.
Of the 54  remaining sites, 33 had in-
sufficient data (i.e. less than 10 observa-
tions during the three month evaluation
period), and 7 were  located in areas that
were classified as industrial.
  With  few exceptions, the hi-vol,
dichotomous and SSI samplers used in
the IPN were only activated once every
six days, at which time  24-hour average
ambient air concentrations were recorded
from  midnight to midnight (LST). When
combined with  the amount of "down
time" experienced  at each site,  these
sixth-day observations resulted in a dearth
of data, which  in turn  made the model
evaluation very difficult and preliminary
at best. Using such a temporally incon-
sistent data set makes the observations
very susceptible to extremes caused by
local sources. The tremendous variability
exhibited by the observed data, whether
real or artificial, cannot be modeled by a
regional-scale, long term (monthly) model
such as RELMAP.
  RELMAP was run on a monthly basis
for July, August and September, 1980 in
order to produce monthly and seasonal
simulations of  concentrations and wet
and dry depositions of fine and coarse
particulate matter. Monthly and seasonal
simulated values of fine and coarse con-
centrations (expressed  in ng/m3) were
compared to the 14 compatible sites from
the IPN. The  correlation between the
simulated and observed values of fine
particulate matter was 0.533, indicating
that 28.4% of the variance experienced
by the observed values could be accounted
for by the simulated values. Likewise, the
correlation  between the observed and
simulated coarse  concentrations  was
0.322, indicating that 10.4% of the vari-
ance could be explained by the simulation.
  The standard residuals  ((observed-
predicted)/observed) for each of the in-
dividual  sites for  the entire summer
indicate that the model consistently un-
derpredicts across  the entire evaluation
network. Standardized  residuals range
between 0.42 and 0.89 for the fine con-
centrations and between 0.48 and 0.93
for the  coarse concentrations. This
significant underprediction exhibited by
the model  is  not  surprising  given the
nature of the discrepancies  discussed
throughout this section.


Conclusions and
Recommendations
  In response to the promulgation of the
new, smaller, size discriminate National
Ambient Air  Quality Standards for IP,
RELMAP has been modified to now
include simple, linear parameterizations
simulating  the chemical and physical
processes of fine and coarse particulate
matter. Shifting the emphasis to the
smaller particles enhances the utility of
regional scale, Lagrangian models such
as  RELMAP.  Because  these recently
modified parameterizations are only ac-
curate to a limited degree, they may be
upgraded or even replaced in  the future
with  more sophisticated parameteriza-
tions  as further research is  conducted.
As an initial step in this possible refine-
ment of RELMAP,  the  model was sub-
jected to a sensitivity analysis.
  Simulated concentrations of fine and
coarse particulate matter were found to
be by far most sensitive to changes in the
wet deposition  rates of fine and coarse
particulate matter, respectively. However,
concentrations of fine particulate matter
were quite insensitive to changes in the
wet deposition  rate of SO2. Concentra-
tions of coarse particulate matter were
somewhat  sensitive to dry  deposition
rates of coarse particles, however, fine
particulate  matter  concentrations were
less  sensitive to dry deposition  of fine
particles and highly insensitive to  dry
deposition of S02. And finally, fine par-
ticulate matter concentrations proved to
be somewhat  sensitive  to  the trans-
formation rate of S02 into S04=.
  Future research  should  concentrate
upon refining the parameterizations in-
volving the wet deposition of both fine
and coarse particulate matter. Not only
has wet deposition proven to be the most
influential parameterization employed by
the model, it is also currently the least
understood.
  In  order  to  determine just how  ac-
curately these  new parameterizations
actually simulate  the  physical and
chemical processes of the atmosphere,
RELMAP was subjected to a model per-
formance evaluation, in which simulations
of ambient air concentrations of fine and
coarse particulate matter were compared
to data from the IPN. Unfortunately, in-
adequacies inherent to both the emissions
and  monitoring data sets  limited  the
extent of this evaluation.
  The  NAPAP emissions  inventory was
designed primarily to support acid deposi-
tion  modeling,  not  regional  particulate
modeling.  Because of this, many defici-
encies were found with  the  inventory,
including the following: (1) most open
source emissions were omitted from the
inventory (which by some estimates ex-
ceed 50,000 ktons of TSP),  (2) the esti-
mates  of contributions from paved and
no-paved roads, which account for 70%
of the total inventory, are much lower in
the NAPAP inventory than  other  in-
dependent estimates, (3) a total of 8% of
the NAPAP inventory cannot be fraction-
alized,  because particle size distributions
are not available for many source classifi-
cation codes.
  The only way to alleviate these defici-
encies  is  to reduce the tremendous
amount of uncertainties in the estimates
of the  open source emissions.  Such a
solution may  be forthcoming  as the
NAPAP Task Group II  is scheduled  to
release, in the  fall of  1987,  a revised
emissions  inventory  for open  source

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emissions of TSP.  Should this revised
inventory include the major open sources
of TSP, RELMAP's accuracy and therefore
its credibility as a regional-scale panicu-
late model will improve.
  A  second major  deficiency  that also
proved to be detrimental to the model
performance evaluation  is the incom-
patibility of the IPN data. Like the NAPAP
Version 5.0 emissions inventory, the IPN
was not designed for regional scale par-
ticulate modeling. Because of this, many
obstacles were encountered when trying
to evaluate the model with the IPN data,
including the following: (1) designed pri-
marily to characterize the urban-scale
concentrations of TSP, an overwhelming
majority (144 of 157) of the  IPN sites
were classified as either center city or
suburban; (2) observations were  only
recorded once every sixth day (most sites
also had incomplete records) resulting in
a dearth of data; (3) many of the moni-
toring sites did not  come "online" until
after the evaluation  period; and (4) many
of the sites were  located outside  the
model's domain. The combination of these
deficiencies render  the data inadequate
for evaluating regional scale particulate
models.
  At the present time, there are no plans
to implement a network that would fulfill
the specific needs of regional scale par-
ticulate modeling. However,  in the near
future, a network proposed by NAPAP to
assist in the evaluation of acid deposition
models will begin monitoring pollutants
on a regional scale at between 30 and 50
sites located in the eastern United States.
As currently proposed, the network fails
to address the  needs of regional scale
particulate modeling.
  Since appropriate data bases to evalu-
ate  regional scale particulate models do
not exist, nor  are  any  proposed, and
because  the cost of initiating and oper-
ating a  network are prohibitive,  it is
recommended  that the  operational/
analysis protocol of the proposed NAPAP
network  be  expanded to obtain an  ap-
propriate data base for evaluating regional
scale particulate models. Because of its
spatial and  temporal distribution,  the
NAPAP  network would  provide an  ex-
cellent data base. By supplementing the
proposed network with fine  and coarse
particulate matter monitoring equipment,
an appropriate data base can be generated
for particulate modeling for a fraction of
the cost needed to initiate and operate a
new network.
  Unfortunately, the inadequacies dis-
cussed above have greatly  limited  the
scope of this model evaluation, therefore.
it must be considered preliminary at this
time. Results of the performance evalua-
tion indicate that RELMAP significantly
underpredicted  the average  ambient
concentrations of both fine and  coarse
particulate matter for the three month
period. The observed and simulated fine
concentrations were  22.71  and  7.20
Mg/m3, respectively, while the observed
and simulated coarse concentrations were
14.34 and 2.56 jug/m3, respectively. The
correlation between the observed and
simulated fine and coarse concentrations
were 0.53  and 0.32, respectively. Con-
sidering the nature of the deficiencies
discussed above, such an underprediction
by the model, through disappointing, is
not surprising.  Each of the deficiencies
inherent  to the NAPAP inventory and
several inherent to the  IPN data would
indeed lend themselves to an underpre-
diction by the model.
  In order for RELMAP to become a
credible regional particulate model which
can be used as a tool  in assessing the
effects of various emission adjustment
scenarios, it is critical that: (1) a revised
TSP emissions inventory become available
which  more  accurately emulates  both
the natural and anthropogenic emissions
of TSP,  and (2)  adequate,  regionally-
representative and continuous measure-
ments  of ambient air concentrations of
both fine and coarse particulate  matter
are obtained.
   The EPA  author Brian K.  Eder is  with the Atmospheric Sciences Research
    Laboratory. Research Triangle Park, NC 27711.
   The complete report, entitled "A Sensitivity Analysis and Preliminary Evaluation
    of RELMAP Involving Fine and Coarse Particulate Matter," (Order No.  PB
    88-114 012/AS; Cost: $14.95, subject to change) will be available only from:
    only from:
          National Technical Information Service
          5285 Port Royal Road
          Springfield. VA 22161
          Telephone: 703-487-4650
   The EPA author can be contacted at:
          Atmospheric  Sciences Research Laboratory
          U.S. Environmental Protection Agency
          Research Triangle Park, NC 27711

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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300

EPA/600/S3-87/034
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